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Learn9701Paper 1 · Multiple ChoiceCarboxylic acids and derivativesCarboxylic acids and esters
Carboxylic acids and derivatives · Subtopic 1 of 1

Carboxylic Acids and Esters

Carboxylic acids (RCOOH) are made by oxidising primary alcohols or aldehydes (reflux with acidified dichromate) or hydrolysing nitriles with acid. They are weak acids: react with metals (H₂), bases (salt + water) and carbonates (CO₂: the test that distinguishes them from phenols and alcohols). LiAlH₄ reduces them to primary alcohols. With alcohols and conc. H₂SO₄ they form esters, named alkyl-first (methyl ethanoate). Ester hydrolysis: acid (reversible, gives acid + alcohol) or alkaline (irreversible, gives carboxylate salt + alcohol: saponification). Esters are used as flavourings, solvents and plasticisers; fats are triesters of glycerol.

Cambridge 9701 Paper 1Cambridge 9701 Paper 2Edexcel YCH11 WCH14AQA 7405 Paper 2≈ 45 minRevision 1 · updated 2026-10-30
Section 1 of 14

Learning objectives

  • Describe preparation and reactions of carboxylic acids.
  • Describe esterification and name esters.
  • Compare acid and alkaline hydrolysis of esters.
  • Describe uses of esters, fats and soaps.
Pause and think

Why is alkaline hydrolysis of an ester preferred over acid hydrolysis when making soap?

Section 2 of 14

Core idea

Start hereVinegar to bananas

Ethanoic acid smells sharp; turn it into an ester and you can get the smell of pear drops, bananas or pineapple.

The big idea

Carboxylic acids are weak acids that react with carbonates. With alcohols they form esters; esters can be split again by hydrolysis.

1. Esters

RCOOH+R′OH⇌RCOOR′+H2O\mathrm{RCOOH+R'OH\rightleftharpoons RCOOR'+H_2O}
where
R
acid part (named –oate)
R'
alcohol part (named first, as alkyl)
Ester hydrolysis

Alkaline hydrolysis goes to completion.

Worked examplePercentage yield of an ester

6.06.0 g ethanoic acid (MrM_r 60) with excess ethanol gives 5.285.28 g ethyl ethanoate (MrM_r 88). Find the percentage yield.

Goal
% yield.
Strategy
Theoretical mass from 1 : 1 ratio.
  1. n=6.060=0.100 moln=\frac{6.0}{60}=0.100\ \text{mol}
    Moles of acid.
  2. m=0.100×88=8.80 gm=0.100\times88=8.80\ \text{g}
    Theoretical ester.
  3. 5.288.80×100=60%\frac{5.28}{8.80}\times100=60\%
    Actual over theoretical.
Answer60%.
✓ CheckBelow 100% as expected for an equilibrium ✓.
Common misconceptionNames the wrong way round Methyl ethanoate comes from methanol and ethanoic acid, not the reverse.

Summary

  • Weak acids; CO₂ with carbonates.
  • LiAlH₄ → primary alcohol.
  • Esters: alkyl + –oate.
  • Alkaline hydrolysis → soap.
Key words
Esterification
Acid + alcohol → ester + water.
Saponification
Alkaline hydrolysis of fats to make soap.
Triglyceride
Triester of glycerol and fatty acids.
HistorySoap making. Babylonians made soap around 2800 BC by boiling fats with wood ash, unknowingly carrying out alkaline ester hydrolysis.
Fun factBananas and nail polish. 3-methylbutyl ethanoate smells of bananas; ethyl ethanoate is a common solvent in nail polish remover.
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